FIG. 14 shows a conventional pneumatic tire 2. The tire 2 includes a pair of beads 4 and a carcass 6. Each bead 4 includes a ring-shaped core 8 and an apex 10 extending from the core 8 outward in a radial direction. The carcass 6 extends on and between one of the beads 4 and the other bead 4.
FIG. 15 shows a cross-section of the core 8 of the bead 4. The core 8 includes a cord 12 extending in a circumferential direction. In the bead 4, the core 8 is formed by winding the cord 12 in the circumferential direction a plurality of times.
The tire 2 is fitted onto a rim. When the tire 2 is fitted onto the rim, each bead 4 portion comes into contact with a flange of the rim. As described above, the core 8 is formed by winding the cord 12 in the circumferential direction a plurality of times. The core 8 tightens the rim. Thus, the tire 2 is prevented from being displaced or coming off from the rim.
FIG. 16 shows a state where the tire 2 is fitted onto a rim 14. As shown in the drawing, one bead 4a portion is brought into contact with one flange 16a of the rim 14. The other bead 4b portion is dropped into a drop 18 of the rim 14. Air is injected into the space surrounded by the inner surface of the tire 2 and the rim 14, whereby the other bead 4b portion comes into contact with the other flange 16b. Accordingly, fitting the tire 2 onto the rim 14 is completed. The pressure of the air injected during fitting is referred to as fitting pressure. The fitting pressure influences ease of fitting the tire 2 onto the rim 14. Various examinations have been made in order to reduce the fitting pressure. One example of the examinations is disclosed in JP2002-36830.